1. Field of the Invention
The present invention relates to regulators that are used in apparatuses requiring stable start-up, and more particularly, to a regulator with soft-start using a current source that can reduce noise and extend battery life by implementing soft-starting by using a current source to cause a predetermined amount of current to flow through a power switch at initial power up.
2. Description of the Related Art
In general, an external voltage of 3V is applied to IC devices. When an IC device has a core with a voltage of 1.8V, a voltage of 3V needs to be converted into a voltage of 1.8V by using a regulator. This regulator will be described with reference to FIGS. 2 and 3.
FIG. 1 is a conceptual view illustrating a regulator according to the related art.
A regulator, shown in FIG. 1, includes a power switch 10, a load capacitor CL, and a discharge switch SW. The power switch 10 is connected to a power supply Vcc to supply a current I. The load capacitor CL is charged with charges by the current I from the power switch 10, and outputs a predetermined voltage. The discharge switch SW is used to discharge the voltage charged in the load capacitor CL since an output voltage of the regulator needs to be a zero voltage in order to prevent a leakage current generated when the regulator is turned off.
The operation of the regulator according to the related art will be described with reference to FIGS. 1 and 2.
FIG. 2 is a view illustrating the operation of the regulator according to the related art. Referring to FIGS. 1 and 2, when the power switch 10 is turned on, a sudden surge of current is caused from the power supply Vcc to the load capacitor CL. Thus, a maximum current Imax flows at a predetermined time t1, and the largest amount of current is consumed. Here, the load capacitor CL is charged up to a predetermined voltage.
Then, when the regulator, shown in FIG. 1, is reset, the power switch 10 is turned off, and at the same time, the discharge switch SW is turned on to discharge the voltage charged in the load capacitor CL. Then, when the power switch 10 is turned on, and the discharge switch SW is turned off, as described above, a sudden increase of current is caused from the power supply Vcc to the load capacitor CL. The maximum current Imax flows at the predetermined time t1, and the largest amount of current is consumed. At this time, the load capacitor CL is charged up to the predetermined voltage.
However, in a case of the output voltage Vout that may be, for example, 1.8V, the load capacitor having a large capacitance value is used to remove ripple or noise as described above. When a voltage of 1.8V is output while the load capacitor is charged or discharged, a large amount of current is instantaneously consumed through the load capacitor at initial start-up.